Electronic imaging or scanning systems are commonly used to transform an image on an image-bearing surface from one form, such as a paper original, to an electronic form, such as a digital or analog signal. Once an image is converted to an electronic form, many uses of that signal become possible, including, without limitation, the reproduction of the image onto a piece of paper, the projection of the image onto a video display terminal, the transmission of the image to a remote location, and the further processing of that image, such as by a computer, an optical pattern recognition device, or the like.
Electronic imaging systems typically include an array of photosensitive elements, such as photosensors, and a light source operatively disposed relative thereto so as to provide illumination of the surface being scanned. In those instances where a linear array of photosensitive elements is employed, it is necessary that either the image on that surface is moved in a direction perpendicular to the longitudinal axis of the linear array, or the linear array of photosensitive elements is moved in a direction perpendicular to the longitudinal axis of that surface. Alternatively, in those instances where a two dimensional array of photosensitive elements is employed, the entirety of the document may be instantaneously scanned without the need for initiating relative motion therebetween. Regardless of whether linear or two dimensional arrays of photosensitive elements are employed, the light reflected from the image-bearing surface varies depending upon the image on any small area portion of the surface being scanned; i.e., a darker small area portion of the surface will cause the photosensitive elements to receive less reflected light, while a brighter small area portion of the surface will cause the photosensitive elements to receive more reflected light. Since the photosensitive elements are adapted to effect a detectable change in the electrical conductivity thereof in response to the receipt of differing amounts of incident radiation, the change in conductivity can be detected and relayed in the form of electrical signals.
It should be appreciated by those ordinarily skilled in the art that electronic image scanning systems are of great commercial utility insofar as they permit the conversion of human readable data into electronic format, which format is compatible with various electronic processing, transmission and storage operations. Accordingly, electronic image scanners have gained acceptance in such diverse fields as publishing, finance, engineering, telecommunications and the graphic arts. Since electronic image scanners are essentially the "eyes" of data processing systems, their ubiquity should be as great as that of the desk-top computer terminal; however, such is not the case at the present point in time owing in part, to the expense, size and limited scanning capacity of heretofore available scanning systems.
The assignee of the subject invention has already developed large area electronic image scanners which are specifically adapted to reproducibly scan a pattern of information on a drafting table or a marker board and produce a digital signal corresponding thereto. Such large area scanners are disclosed in commonly assigned U.S. patent application Ser. No. 885,907 filed July 15, 1986 and entitled "Photosensitive Line Imager Utilizing A Movable Scanning Arm", now U.S. Pat. No. 4,725,889, the disclosure of which is incorporated herein by reference. Applicants, have also, in aforementioned U.S. patent application Ser. No. 111,234, developed a portable, small electronic image scanner which is relatively simple to operate and fairly inexpensive to produce. While such contact-type image scanning apparatus have been made commercially available as an adjunct to personal computing systems and the like, the use thereof for purposes of transmitting the digital signals photogenerated by the array of thin film photosensitive elements associated therewith to integrated copying systems for providing hard copy reproductions of images on image-bearing surfaces has yet to be commercialized.